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Abstract:
Earthquake ground-shaking recorded at the surface is influenced by local site conditions. At stiff sites and for small ground motions, this soil response behaves linearly, at soft sites and for larger ground motions, however, the site effects starts to become nonlinear. The complex phenomena of nonlinear site-amplification remain a challenge in seismic hazard assessment, mainly because there are still few recorded observations. In this study we use the comprehensive Japanese KiK-net network to systematically capture the empirical effects of nonlinear soil response. Here the nonlinear soil-response is measured in the stations’ surface-to-borehole ratios as the change in amplitude and shift in frequency between strong-motion events and the linear site-response. We then derive station-specific parameters for nonlinearity using the measurements for each station and explore the correlation between the station nonlinearity and a selection of geotechnical and geological parameters. Our results show that finding site parameters suitable for predicting nonlinear site-effects remain challenging as the nonlinear soil-behavior is largely site specific.
